Alternating current voltage regulator



July 10, 1956 H. F. MAYER 2,754,471

ALTERNATING CURRENT VOLTAGE REGULATOR Filed April 15, 1953 aaour INVENTOR. HHEEY F NHYCE BY u MD 197' 7 OBNE Y5 United States Patent ALTERNATING CURRENT VOLTAGE REGULATOR Harry F. Mayer, Clinton, N. Y., assignor to the United States of America as represented by the Secretary of the Air Force Application April 15, 1953, Serial No. 348,872 '8 Claims. Cl. 323-435 This invention relates to an alternating current voltage regulator and particularly one in which a variable transformer is used and controlled with a switching means to effect bucking or boosting the line voltage thus doubling the control range.

In the present invention a transmission line having a voltage to be regulated is coupled to a variable transformer that is in many respects similar to a Variac but having two separate windings, a fixed primary winding rated at the transmission line voltage and a secondary winding with a sliding tap rated at some voltage value of one-half the corrective voltage range intended to be used in reglating the voltage in the transmission line. For example, the transmission line may be rated for 115 volts but which may vary as much as 10 volts in which case the primary would be rated at 115 volts and the secondary at 5 volts. Through a switching arrangement, automatically operated when the adjustable tap has passed through its full range of 5 volts, the primary is reversed as well as a primary to a second transformer supplying current to the heaters of a tube control circuit. The heaters of the tube circuit are part of a bridge circuit controlling the tube circuit which in turn controls a motor for moving the adjustable tap. When the switching means is thrown, as when the adjustable tap has reached its Zero position of control, the primaries of both transformers are reversed and the motor circuit is reversed to provide an additional range of the variable transformer, and using the example, through an additional 5 volts which permits a regulation within the range of volts to the transmission line. It is therefore a general object of this invention to provide an alternating current transmission line to maintain a constant alternating current voltage on the transmission line under prescribed limits of variation of load, supply voltage, and frequency by the use of a variable transformer in the transmission line actuated by a control motor through a circuit arrangement responsive to variations in voltage from the rated voltage, the variable transformer and circuit arrangement having switching means related therewith to effect bucking or boosting of the transmission line voltage doubling the range of the variable transformer.

These and other objects, advantages, features, and uses will become more apparent as the description proceeds when taken in view of the accompanying drawing diagrammatically showing the circuits and elements illustrating the invention.

In the drawing the alternating current transmission line is represented by the reference characters 1 and 2. A variable transformer, generally represented by the reference character 3, has its primary winding 4 connected across the transmission line through the double pole, double throw switch 5, later to be described, by lead 6 connected'to the low line 2 and by the lead 7 connected to the line 1 on the output side of the voltage regulator. The primary winding 4 is rated for the same voltage as the transmission line 12. The secondary winding 8 of the variable transformer 3 is directly connected to 2,754,471 Patented July 10', 19581 ice one of the transmission lines and usually the high line 1 at one end thereof, the opposite end of this winding being open. An adjstable tap 9 is connected directly to the high line 1 on the output side of the regulator such that the line 1 is directly connected through the secondary winding 8 and adjustable tap 9. The adjustable tap 9 is actuatable by a direct current electric motor 10 through shafting 1-1 or other positive mechanical means in any well known manner. The adjustable tap 9 has extension means 12 thereon operable to actuate the switch 5 in the zero voltage limit of the tap 9, at which time it is at the junction of the high line 1 and the winding 8, and to actuate a limit switch 13 to the open position in the upper voltage limit thereof, later to be described. The switch 5 is shown actuatable through the linkage 14 although in actual practice switch 5 is the alternately thrown type in which each press of the actuator 14 throws the switch whereby the switch 5 may be actually positioned adjacent the adjustable tap 9. Switch 5 may be thought of as similar to the foot operated light swith of the modern automobile.

In the connection through the switch 5 the primary winding 4 is connected to the poles 15 and 16 while the switch blades 17 and 18 are each connected to the transmission line by conductors 6 and 7. The opposite poles 19 and 20 of the switch 5 are cross connected to poles l6 and 15, respectively, so that line 2 can be alternately connected to pole 15 or 16 and line 1 similarly will be connected simultaneously with pole 16 or 15, respectively, thus causing reverse polarity of the primary winding 4 upon switch 5 actuation whereby the induced voltage in the secondary winding '8 will either boost or buck the transmission line voltage by an amount determined by the adjustable tap 9.

The poles 19 and 20 of the switch 5 are connected to a primary winding 21 of a filament transformer 22, the secondary 2324 of which is center tapped to ground. The left half winding 23 connects the filaments 25, 26, 27, and 28 in series in four tubes 30, 31, 32 and 33 to the grid of tube 30. The right half winding 24 is connected to the grid of tube 30 through an adjustable resistor 34. The secondary windings 23-24, tube filaments 25-28, and adjustable resistance 34 form a bridge circuit in which the adjustable resistance 34 can be made to match the resistance of the filaments 2528 for the desired voltage level to be obtained by the regulator, as will appear later in the description.

The triode tubes 30 to 33 each have their cathode connected to ground, tubes 31 to 33, each having a resistor 36, 37, and 38, respectively, in the ground connection. The anodes of tubes 30 and 31 are each connected to a plate supply source through resistors 39 and 46, respectively. The anodes of tubes 32 and 33 are each connected to the high transmission line as 1 through a conductor 41 with an electromagnetic coil 42 and 43, respectively, in each anode circuit. The anode of tube 30 is coupled to the grid of tube 31 through a condenser 44 and to the cathode of tube 31 through the resistor 45. The anode of tube 31 is coupled through a condenser 46 to the grid of tube 32 and through a resistor 47 to the cathode of the latter tube. The cathode of tube 31 is coupled to the grid of tube 33 through the condenser 48. The bridge output is amplified in tube 30 and phase-inverted in tube 31 to supply the triode tubes 32 and 33.

The electromagnetic coil 42 is operable to actuate a normally open double pole, single throw switch 54 and the electromagnetic coil 43 is operable to actuate a double pole, double throw switch 51. Switch blades 52 and 53 are each connected to a direct current voltage source 54 and 55 which voltage source also supplies current to the field 56 of the direct current motor 13. The switch blades 52 and 53 are respectively normally biased in contact with the contacts 57 and 58 which contacts are respectively connected to the contacts 59 and 69 of the switch Stl. Contacts 61 and 62 are each connected directly to the armature posts 63 and 64, respectively, of the motor It), the contact 61 being opposite to contact 57 and the contact 62 being opposite to the contact 53 whereby switch blade 52 normally rests against contact 57 and is operable to connect the contact 61 simultaneously with the operation of switch blades 53 connecting with contact 62 which switch blade 53 normally rests against contact 58. Switch blade 63 of the switch St; is directly connected with the armature post 64 of the motor in while the companion switch blade 65 is connected by conductor 66 through the normally closed limit switch 13 to the armature post 63. It may now be realized that the switching circuits just described are operable to switch the motor 10 on or E and to control the rotative direction of the motor ill. With the switches 50 and 51 resting in their normal position as shown the motor it} will be still since the armature current is broken at the switch 54 Upon the energization of coil 43 switch 51 will be thrown to directly connect the motor armature in the direct current circuit. Since only one of the electromagnetic coils 42 and 43 can be energized at any one time, switch t; remains as shown. The motor will rotate in one direction. Upon the energization of the coil 42 (coil 43 now being deenergized) the switch it? will be thrown connecting the armature posts in the reverse direction from that connected by switch 51 to cause the motor 10 to rotate in the reverse direction unless limit switch 13 is open.

in the operation of the voltage regulator let it be assumed for the purpose of example that the transmission line is rated at 115 volts which may vary 4 to 5 volts above or below this voltage level, although the regulator is quite practical and useful for other rated voltage transmission lines, whether single phase or multi-phase. As long as the voltage remains at 115 volts the regulator will be inoperative and the adjustable tap 9 will rest at its zero voltage position near the juncture of the line 1. At this point the adjustable resistance 34 is positioned at a point where the resistance therethrough is exactly equal to the resistance through the four tube filaments -28 at which time the bridge circuit is balanced and thus the tube circuit is inactive. Any output transmission line voltage of desirable higher or lower value can be obtained by adjustment of the resistance 34 accordingly. if the supply transmission line voltage should rise the filaments 2528 would become hotter increasing the resistance in this side of the bridge circuit. The unbalance in one direction in the bridge circuit produces an alternating voltage on the grid of the tube fall which is amplified on the anode thereof. The alternating anode voltage is impressed on the grid of the phase-inverter tube 31 as well as on the grid of the tube 33. The alternating anode voltage of the phase-inverter tube 31 is impressed on the grid of the tube 32, the alternating voltages on the grids of tubes 32 and 33 being out of phase. The anodes of the tubes 32 and 33 being connected to the high line 1 each have the alternating voltage of the transmission line impressed on themin phase. Whichever tube 32 or 33 has the grid voltage in phase with the anode voltage will cause conduction if the input voltage at the grid of tube 3% is strong enough. For the example, a rated 115 line voltage given, a difference of .2 of a volt (plus or minus) in line voltage will be sutticient to activate the electronic tube circuit and cause the in-phase tube 32 or 33 to conduct. While the tube circuit and switch means Ell, 51 may be set either way to get proper results, let it be said for the purpose of illustration that tube 32 is the in-phase tube which becomes conductive to actuate switch 5% to produce motor rotation to advance the adjustable tap 9 counterclockwise which increases the number of turns in the secondary winding 8 to the transformer relation with the primary winding 4. Let it also be as sumed that the switch 5 is resting as shown; that is, the blade is across 15 and 17 and across 16 and 18 in which position the primary winding 4 is setting up a flux relation with the secondary winding 8 to buck or reduce the line voltage to the desired 115 volts at which time the bridge circuit is again in balance and the tube circuit and motor become inactive. If the secondary winding 8 is rated, for example, at 5 volts and the line voltage should for some reason go above 120 volts, the adjustable tap would proceed counterclockwise whereupon the extension 12 would open the limit switch 13 to cut the motor it} off. At any time that the voltage should again come back to within the 120 volt range the bridge circuit would be unbalanced in the other direction to cause tube 33 to bein phase which will set the switch 51 for operation of the motor it to rotate the adjustable tap 9 in the clockwise direction.

If the line voltage continues to fall and goes below 115 volts, the motor 10 will continue to operate to rotate the adjustable tap 9 in the clockwise direction where the extension 12 will actuate the switch 5 to reverse the connections to the primary windings 4 and 21. This switch reversal causes a reversal in flux relation of the primary winding 4 with the secondary winding 8 to boost the line voltage by an amount up to 5 volts that the line voltage falls below 115 volts. The reversal in the primary winding 21 causes a reversal in the bridge circuit to efiect a phase relation in the grids of the tubes 32 and 33 with the anodes thereof to reverse the direction of the motor 10 to adjust the adjustable tap 9 in accordance with the voltage boost required to bring and maintain the line voltage up to 115 volts. Any dip in line voltage below volts will cause the limit switch 13 to be actuated in like manner as for excessive line voltage above 120 volts to break the circuit to the motor iii. The line voltage on the output side will thus be maintained at a fixed value of volts although the supply line voltage may vary up or down from 110 to volts. Voltage variations outside these limits causes the operation of the limit switch which protects the regulator from damage.

While the above described invention of the illustrated form thereof in the drawing is a preferred form, it is to be understood that other modifications and changes may be made without departing from the spirit and scope of this invention and I desire to be limited only by the scope of the appended claims.

I claim:

1. An alternating current voltage regulator for connection to an alternating current transmission line comprising: a variable transformer having the primary thereof connected across the transmission lines to be regulated and the secondary thereof connected in series with one of said transmission lines through an adjustable tap; a reversing switch in said primary connection having an alternate switch throwing actuator operable to be actuated by said adjustable tap at its zero voltage adjusting position; and means for controlling said adjustable tap over the variable voltage range, said reversing switch being operable thereby to reverse the polarity of said primary to said secondary to cause the adjusted voltage to buck or to boost the transmission line voltage; said means for controlling said adjustable tap being an electric motor mechanically coupled to said adjustable tap, and a related electric system responsive to voltage changes above or below the rated voltage of the transmission line to be regulated, said electric system including a fixed transformer with the primary thereof connected to said transmission line through said reversing switch whereby the polarity thereof changes simultaneouslywith the changes in polarity of said variable transformer primary, with the secondary of said fixed transformer forming a bridge circuit which remains in balance for the rated transmission line voltage and which is unbalanced in either direction by deviations in rated transmission line voltage and is operative in the electric system to control the energization and rotative direction of said motor to adjust the transmission line voltage.

2. An alternating current voltage regulator as set forth in claim 1 wherein the operation in said electric system to adjust transmission line voltages is accomplished by a tube circuit responsive to voltages resulting from bridge circuit unbalance and to the phase relation of said unbalanced bridge voltages to that of the transmission line, one tube being conductive in one condition of phase relation to cause motor rotation in one direction, and another tube being conductive in another condition of phase relation to cause motor rotation in the other direction to correct transmission line deviations from rated voltage in another direction.

3. An alternating current voltage regulator as set forth in claim 2 wherein each last mentioned tube has a switch means in its anode circuit which switch means of each tube controls a circuit to said motor for each rotative direction thereof, said switch means controlling said motor circuit in a motor direction to drive said adjustable tap toward the end of said secondary winding of said variable transformer including a limit switch in the motor circuit to stop motor rotation when said adjustable tap reaches the end of said secondary variable winding.

4. In an alternating current voltage regulator for connection to an alternating current transmission line comprising; a variable transformer having the primary winding thereof connected in parallel with the transmission line to be voltage regulated and having the secondary thereof connected in series with one side of the trans mission line through an adjustable tap; means to reverse the polarity of said variable transformer primary winding operable by said adjustable tap in its position adjacent the connection of said secondary to said transmission line whereby said adjustable tap is operable to regulate the transmission line voltage within limits of twice the voltage range of said secondary, one voltage range being in one polarity condition of said primary providing a boosting adjusted voltage in said secondary and the other voltage range being in another polarity condition of said primary providing a bucking adjusted voltage in said secondary; and means associated with said adjustable tap responsive to deviations in transmission line voltage from rated voltage for adjustably moving said adjustable tap for maintaining the rated transmission line voltage.

5. An alternating current voltage regulator as set forth in claim 4 wherein said means associated with said adjustable tap responsive to deviations in transmission line voltage includes a voltage sensing device for sensing voltage deviations in the transmission line above and below the rated voltage and a reversible electric power means mechanically coupled to said adjustable tap, said voltage sensing device being coupled to said reversible electric power means for energizing said electric power means to adjust said adjustable tap in proportion to the transmission line voltage deviations whereby the transmission line rated voltage is maintained on the output side of the voltage regulator.

6. An alternating current voltage regulator for connection to an alternating current transmission line comprising; a variable transformer having the primary winding thereof connected in parallel to the transmission line to be regulated and having the secondary thereof connected in series with one side of the transmission line through an adjustable tap for regulating the voltage on the output side of the transmission line within the limits of said secondary winding; a reversing switch in said connection of said primary actuable by said adjustable tap for reversing the polarity of said primary with respect to said secondary for causing said primary to buck or to boost the adjusted voltage induced in said secondary; an electronic circuit having an amplifier, a phase-inverter, and a pair of high conduction tubes, the latter pair of tubes having their anodes each coupled through an electromagnetic actuator of a switch to the transmission line; a fixed transformer having the primary winding thereof connected in parallel with the transmission line through said reversing switch and the secondary winding thereof centrally grounded and forming two legs of a bridge ciremit, a third leg connected in series to the heaters of the tubes in said electronic circuit, and the fourth leg connected through an adjustable resistance for adjusting the output voltage of the regulator, the junction between said third and fourth legs being connected to said amplifier for amplifying any voltages representing an unbalance of said bridge circuit, said unbalancing voltages being passed through said phase-inverter to one of said high conductive tubes and being also passed from said amplifier to the other high conducting tube whereby the high conductive tube having the anode voltage in phase with the amplified voltage input from said bridge circuit will be rendered conductive; and a reversible electric power means mechanically connected to drive said adjustable tap and electrically connected to an electric power source through said switches of said electromagnetic actuator, each switch controlling one direction of movement of said electric power means whereby any fluctuation in transmission line voltage from the voltage established by said variable resistance produces bridge circuit unbalance in one direction causing one of the high conductive tubes to become conductive to switch said reversible electric power means producing adjustable tap repositioning to maintain the established voltage, the reversing switch being reversible by the adjustable tap to provide a voltage limit of regulation double the voltage range of said secondary of said variable transformer.

7. A voltage regulator for an alternating current transmission line comprising a transformer having its primary connected across said line through a phase reversing switch and its secondary connected in series with said line through an adjustable tap, a motor coupled to said tap for adjusting it in either direction, control means for said motor comprising means responsive to a departure of the voltage across said primary from a predetermined value to operate said motor in a direction determined by both the direction of said departure and the phase of the voltage across said primary, and means actuated by said adjustable tap at its minimum voltage limit for operating said phase reversing switch.

8. Apparatus as claimed in claim 7 in which there are provided additional means actuated by said adjustable tap at its maximum voltage limit for disabling said motor against further movement of said tap in the voltage increasing direction.

References Cited in the file of this patent UNITED STATES PATENTS 1,414,652 Kirke May 2, 1922 1,947,197 Garman Feb. 13, 1934 2,239,768 Artzt Apr. 29, 1941 2,453,451 Moseley Nov. 9, 1948 

